The human heart is enveloped within a tissue structure referred to as the pericardium, which comprises two major parts. The inner layer of the pericardium lies immediately over the myocardium (heart muscle) and is referred to as the visceral pericardium or epicardium. The outer layer, forming a sac around the visceral pericardium, is referred to as the parietal pericardium. Normally these two layers lie in close contact with each other and are separated only by a thin layer of pericardial fluid, which allows the heart to move within the parietal sac with minimal friction. The potential space between the visceral and parietal pericardia is referred to as the pericardial space. The visceral pericardium is commonly referred to as the epicardium and the parietal pericardium is commonly referred to as the pericardium. This naming convention will be used herein.
Access to the pericardial space is necessary for a variety of medical procedures, including treatment of infections, injuries, and heart defects. For example, cardiac rhythm management systems such as pacemakers, implantable pulse generators, and implantable cardioverter defibrillators include electrode bearing leads for sensing and stimulating the heart. These leads can be deployed from inside or outside the heart. In the latter case, the pericardial space is typically traversed to reach the epicardium for lead implantation and attachment.
Part of the challenge in accessing the pericardial space stems from its minimal thickness. When making an incision or perforation in the pericardium, it is preferable to avoid also puncturing the underlying epicardium and damaging the myocardium or a coronary vessel. The close proximity of the epicardium to the pericardium makes this difficult. Another important consideration is the trend toward minimally-invasive surgical techniques, which generally are associated with a host of advantages including lower costs and fewer complications.
There is a need in the art for improved, efficacious methods and devices for penetrating the pericardium and thereby accessing the pericardial space, which minimize the risk of damaging other heart tissues. There is a further need for such methods and devices that are compatible with minimally-invasive surgical techniques.